I never ever pre cook my chicken before grilling.  I do find that chicken breasts tend to dry out on the grill, so I usually use thighs instead.  I put the chicken on a very hot grill, close the lid,  so it cooks slow, and the outside doesn't burn before the inside has a chance to cook thoroughly. Always try to use Kingsford charcoal, as it holds the heat longer and stays lit, where as the other brands tend to burn out before your chicken is cooked.  I put veg oil, salt and pepper on before grilling that way it doesn't stick to the grill.